Cutting oil



Patented Sept. 15, 1942 CUTTING OIL Gus Kaufman, Beacon, N. Y.,assignor, by mesne assignments, to The Texas Company, New York, N. Y., acorporation of Delaware No Drawing. Application March 14, 1939, SerialNo. 261,771

1 Claim.

This invention relates to sulfurized lubricants, such as cutting oils,and more particularly to light colored or transparent cutting oils ofthis character.

Cutting oils as heretofore employed have frequently been composed offatty or animal oils, and blends of mineral oil with fatty oils. It hasalso been proposed to sulfurize blends of animal oil and mineral oil,but in such case, the sulfur is taken up ahnost entirely by the morereactive fatty oil to produce a product in which the sulfur is in stabletightly combined form with the fatty oil and diluted by the mineral oil.Cutting oils have also been prepared by incorporating sulfur directlywith mineral oil, generally under relatively high temperatures andfrequently under superatmospheric pressure to produce a product in whichthe sulfur is sufiiciently combined with the mineral oil as to resistsulfur separation and sedimentation upon storage.

The earlier cutting oils consisting of simple fatty oils or blendsthereof, as well as the sulfurized blends of mineral oil and fatty oilwhere the sulfur is taken up ahnost entirely by the fatty oil, do notpossess the high cutting efficiency demanded by high speed cuttingoperations of the present time. The' same is true of the straightsulfurized mineral oils where the sulfur is stably and tightly combinedwith the mineral oil.

In my copending application Serial No. 180,573, filed December 18, 1937,now U. S. Patent No. 2,167,439, dated July 25, 1939, the production of acutting oil of superior cutting efficiency is described by sulfurizing astraight mineral lubricating oil with uncombined sulfur in the absenceof added fatty oil or other highly reactive cn-' stituents which wouldpreferentially combine with the sulfur, at arelatively low and criticaltemperature range of the order of about 310-360 F. and at atmosphericpressure-to give approximately 2-3% of loosely combined sulfur in themineral oil, and then stabilizing this sulfurized oil against sulfurseparation and sedimentation by the addition of about 2-3% of a fattyoil or a separately sulfurized fatty oil. While such a pi pduct isoutstanding in cutting efliciency and is eminently satisfactory for mostcutting tool operations, it is comparatively dark in color and does notfall under the classification of a transparent cutting oil.

For some time, the trade has been seeking a light colored transparentcutting oil having high cutting efliciency which is particularlysuitable good visibility of the cutting tool and work is required. Whilethere have been scattered products on the market termed transparentcutting oils, these have either been too dark in color to properlyfallunder this classification, or else have been lacking in cuttingefliciency and unsuitable for high speed operations.

It is an object of the present invention to provide a transparentcutting oil which meets the demand both with respect to color andtransparency as well as high cutting efllciency.

I have discovered that a satisfactory transparent cutting oil of thischaracter can be produced by sulfurizing a light colored pale minerallubricating oil under controlled conditions of comparatively lowtemperature and at atmospheric pressure so as to provide about 1,0435%loosely combined sulfur in the oil, and then enhancing the cuttingefiiciency and at the same time stabilizing th sulfurized oil by theaddition of a small proportion of certain oil soluble materials of thecharacter of extreme pressure bases, such as tricresyl phosphate.

In the preparation of my improved product, a mineral lubricating oil orlubricating oil blend, containing light colored pale lubricating oilshaving a Saybolt Universal viscosity at 100 F. of about 100-l80 seconds,is sulfurized by heating with free sulfur in the absence of added fattyoil or other constituents highly reactive with sulfur at a temperatureof about 300-340" F. and preferably about 320 F. for a controlled periodof time. The quantity of sulfur employed is calculated to give aboutl.0-.1.75% of loosely combined sulfur in the mineral oil, such that itis in a condition to provide high cutting efiiciency. The quantity ofsulfur added is above the range which will enter into simple solution ina light colored pale oil; and the composition is to be distinguishedfrom a simple solution or suspension of sulfur in mineral oil which inconcentrations of about 1% or more of sulfur will not withstand storageat low temperatures without sedimentation, even in the presence ofstabilizers. The temperature and time of heating are critical and arefound to lie within the limits of about 300-340 F. with a period ofheating of from about 1-4 hours at the upper temperature specified, in'order to give-a product of good color with a light colored pale oil inwhich the sulfur is actually reacted with the mineral lubricating forcertain specialized cutting operations where oil in a loosely bound formpossessing the required high cutting eihciency, and yet can bestabilized against objectionable sulfur sedimentation upon storage atlow temperatures by the addition of small amounts of effectivestabilizers of this invention.

To the sulfurized mineral oil prepared as above described, andcontaining sulfur in a loosely bound form, is added a material whichdissolves in lubricating oil to a clear light colored solution, whichpossesses extreme pressure properties, and which functions as astabilizer for the sulfurized mineral oil. Satisfactory materials ofthis type are the organic phosphate and phosphite esters, such astricresyl phosphate, tricresyl phosphite, triphenyl phosphate, triphenylphosphite, dibutyl phosphate and dibutyl phosphite. Other suitableextreme pressure bases may be employed, such as halogenated orchlorinated aromatic or aliphatic compounds of the character ofchlorinated diphenyl, chlorinated fats and fatty oils, chlorinated wax,and sulfurized diphenyl. Any suitable material known in the art topossess extreme pressure properties and which satisfies the requirementsset out above may be employed. Of the materials listed, tricresylphosphate is preferred from the standpoint of eflectiveness,availability and cheapness of product. The extreme pressure base ormaterial is generally added in the proportion of about 13% andpreferably about 1-1.5%. The extreme pressure material may be addedfollowing the sulfurization of the mineral oil and while the same isstill at an elevated temperature. Or the extreme pressure material maybe first admixed with the mineral oil and then the mixture sulfurizedunder the conditions set out above.

In order to further disclose the invention, the following example isgiven, it being understood that the example is merely for purposes ofillustration and the invention is not restricted thereto:

A blend of 135.6 pounds of 100 E pale oil and 67.8 pounds of 180 C paleoil was used. These oils were light colored paraflin base lubricatingdistillates having the following tests respectively:

100 E pale 180 C pale oil oil Gravity 28. 8 27. 1 Flash 350 375 Fire 395435 Viscosity at 100 F., S. U 98 184 Pour F 20 20 Color-Lovibond 95/130/6" i temperature. The mix was then allowed to cool gradually forseveral hours and was drawn off through a 100 mesh screen to remove anysuspended solids. The resulting product was a light pale oil having thefollowing tests:

Gravity A. P. I 27.3 Viscosity at 100 F., S. U 119 Color-Lovibond cell35 Sulfurper cent 1.15 Tricresyl phosphate-per cent 1.0

In a freezing test wherein the product was main tained for 120 hours at3035 F., it showed a slight wax cloud but no sulfur separation. Cuttingtests showed it to be comparable in efficiency to the best cutting oilson the market, including the dark colored products of high sulfurcontent which are too dark to be classified under transparent cuttingoils.

While the combination of the extreme pressure base with the sulfurizedmineral oil prepared as set out above gives this superior type oftransparent product having high cutting emciency, it is found that thesimple addition of these extreme pressure bases to a pale mineral oil ofthis character, even in substantial proportions, does not produce acutting il possessing satisfactory cutting efliciency.

As pointed out above, higher percentages of added sulfur than about 1.5%may not as a rule be loosely combined with a pale lubricating oil toproduce a light-colored transparent cutting oil which can be stabilizedagainst sulfur separation on storage at low temperatures. However, Ihave further found that a transparent cutting oil of satisfactory colorbut containing a higher percentage of overall sulfur content can beproduced by sulfurizing a high sulfur containin distillate lubricatingoil of pale color. For example, a distillate lubricating oil containingabout 1.5-3.5% of naturally ccurring sulfur, while not possessing highcutting efficiency such as to be suitable for a cutting oil of this typein its naturally produced state, can be sulfurized under substantiallysimilar conditions to those set out above with about 0.8-1.5% of addedfree sulfur to give a highly effective product having an overall sulfurcontent of about 2.3-5.0% sulfur, and which is stable against sulfurseparation and sedimentation by the use of similar quantitles of theextreme pressure bases set out above. Consequently, where specificationscall for a transparent cutting oil of reasonably good color having highsulfur content and which is suitable for high speed cutting operations,such a product is prepared from a high sulfur containing distillatelubricating oil of this character. As an example of a cutting oil ofthis type, the following is given. A so-called Sultal viscosity stock,which is a dewaxed high sulfur containing distillate lubricating oil ofpale color from a naphthene base or Coastal crude, was selected havingthe following tests:

Viscosity at 100 F., S. U Pour, F +15 Coldr-Lovibond 10 Sulfurper cent2.53

Gravity, A. P. I 23.6 Viscosity at 100 F., S. U 106 Color-Lovibond cell,25 Sulfur, per cent 3.61 Tricresyl phosphateper cent 1.0

In a freezing test at 30-35 F. for hours,

only a slight cloudiness developed but no sulfur better than the mosteflective cutting oils now on the market.

Obviously many modifications and variations of the invention, ashereinbefore set forth, may be made without departing from the spiritand scope thereof, and therefore only such limitations should be imposedas are indicated in the appended claim.

I claim:

A transparent cutting oil of good color conslsting essentially of a palemineral lubricating oil initially containing about 15-35% ofnaturally-occurring sulfur and sulfurized by heating with sulfur in theabsence of added fatty oil under temperatures of about 300-340" F. andat substantially atmospheric pressure to produce a' loosely combinedsulfur content providing an overall sulfur content in excess of about2.3% and less than about 5.0%, and stabilized with about 1 -3% of anextreme pressure material selected from the group consisting ofchlorinated diphenyl, chlorinated fats, chlorinated fatty oils,chlorinat- GUS KAUFMAN.

